As pointed out in the comments below, it's not recommended to attach events to the scroll event - as the user scrolls, it fires A LOT, and can cause performance issues. Consider using it with Ben Alman's debounce/throttle plugin to reduce overhead.

For those browsers that do support "position: fixed" you can simply use javascript (jQuery) to change the position to "fixed" when scrolling. This eliminates the jumpiness when scrolling with the $(window).scroll(function()) solutions listed here.

Beautiful! Your solution was 99%... instead of "this.scrollY", I used "$(window).scrollTop()". What's even better is that this solution only requires the jQuery1.2.6 library (no additional libraries needed).

The reason I wanted that version in particular is because that's what ships with MVC currently.

If you are looking for an option that does not require much JavaScript (and and all the problems that come with it, such as rapid scroll event calls), it is possible to gain the same behavior by adding a wrapper <div> and a couple of styles. I noticed much smoother scrolling (no elements lagging behind) when I used the following approach:

//Compensate for the scrollbar (otherwise #fixed will be positioned over it).
$(function() {
//Determine the difference in widths between
//the wrapper and the scroller. This value is
//the width of the scroll bar (if any).
var offset = $('#wrapper').width() - $('#scroller').get(0).clientWidth;
//Set the right offset
$('#fixed').css('right', offset + 'px');​
});

Of course, this approach could be modified for scrolling regions that gain/lose content during runtime (which would result in addition/removal of scrollbars).